1. Field of the Invention
The present invention relates in general to an apparatus for driving an LCD panel. More particularly, the present invention relates to an apparatus for self-diagnosing a video signal in an LCD(Liquid Crystal Display) which determines whether or not the video signal is in trouble.
2. Description of the Related Art
FIG. 1 is a block diagram representing a conventional circuit for driving an LCD panel.
Referring to FIG. 1, the conventional circuit for driving the LCD panel includes a micro-controller 130, a receiver 110, a scaler 120 and an interface unit 140. The driving circuit receives an analog video signal from a transmitter 102 of a PC 100, converts the analog video signal into a digital video signal, and transmits the converted video signal to the LCD panel 150.
Specifically, the receiver 110 receives the analog video signal from the PC 100 and converts the analog video signal into the digital video signal, which is composed of digital Red (R), Green (G) and Blue (B) color signals of 8 bits. In general, the receiver 110 includes a video pre-amplifier, an analog-to-digital (A/D) converter and a phase locked loop(PLL) circuit, and is fabricated into one chip.
Next, the scaler 120, which is a digital video processor, converts the digital video signal from the receiver 110 to match the resolution of the video signal with that of the LCD panel. For example, if the input signal to the scaler has a resolution of 800*600 and the resolution of the LCD panel is 1024*768, the scaler scales up the input video signal accordingly.
Generally, the LCD panel adopts an interface format of TTL, LVDS or TMDS, and the interface unit 140 converts the output signal of the scaler 120 to match the interface format adopted by the LCD panel.
The micro-controller 130, which is called a system controller or microcomputer, receives horizontal and vertical sync signals from the PC 100 and signaling equipment, and discriminates an operation mode of the LCD panel from the sync signal and horizontal and vertical frequencies. The micro-controller reads and recognizes mode data stored in a non-volatile memory(not illustrated), and adjusts the operation mode data by controlling an LCD driving circuit.
The micro-controller 130 receives the sync signal from the receiver 110, checks the operation mode from the sync signal and controls the power supply to the inverter 170 and the LCD panel 170 via a power switching unit 160.
The conventional circuit for driving the LCD panel as described above has the problem; it cannot properly detect the trouble state of the scaler 120 and receiver 110. Especially, when a specified bit of digital R, G, B color signals is not processed properly, a user cannot easily detect the trouble.
Accordingly, it is an object of the invention to provide an apparatus which can detect -the trouble state of the receiver 110 and scaler 120.
Another object of the present invention is to provide an apparatus for self-diagnosing a video signal which can detect whether a specified bit of R, G, B color signals is in trouble.
According to the invention, it may be easily detected if the video signal displayed on the LCD panel has been correctly converted. Therefore, the user can self-diagnose the video signal in the LCD panel.
In one aspect of the present invention, there is provided an apparatus for self-diagnosing a video signal to be displayed in an LCD panel. The apparatus includes a receiver, a scaler, a micro-controller, a diagnosis transmitter and a switching unit.
The receiver receives an analog video signal, and converts the analog video signal into a digital video signal.
The scaler converts said digital video signal from the receiver into a format suitable for the LCD panel.
The micro-controller outputs a switching control signal which represents either a self-diagnosis mode or a normal-operation mode as the operation mode of an LCD driving circuit, and outputs a test video signal having a predetermined display pattern if the switching control signal represents the self-diagnosis mode.
The diagnosis transmitter converts the test video signal into an analog signal.
The switching unit transmits the video signal outputted from the PC to the receiver if the operation mode of the LCD driving circuit is in normal operation mode, while it transmits the test video signal outputted from the diagnosis transmitter to the receiver if the operation mode of the LCD driving circuit is in self-diagnosis mode.
Therefore, the micro-controller detects whether or not the video signal is in trouble by comparing the test video signal from the micro-controller with the video signal processed by and fed back from the receiver and scaler if the operation mode of LCD driving circuit is the self-diagnosis mode.
In another aspect of the present invention, there is provided a method of self-diagnosing whether the video signal is in trouble in an LCD panel. The method comprises the steps of:
(a) providing a digital test video signal having a predetermined display pattern through a micro-controller of an LCD driving circiut;
(b) feeding back the test video signal to the micro-controller via an A/D converter, a receiver and a scaler; and
(c) determining whether or not the test video signal is in trouble by comparing the test video signal from the micro-controller with the video signal fed back to the micro-controller.
In a third aspect of the present invention, there is provided a method of self-diagnosing whether the video signal from a PC to an LCD panel is in trouble. The method comprising steps of:
(a) providing a switching control signal through a micro-controller of an LCD driving circuit, said switching control signal representing an operation mode of the LCD driving circuit composed of a self-diagnosis mode and a normal operation mode;
(b) if the operation mode is the self-diagnosis mode,
providing a test video signal having a predetermined display pattern through the micro-controller,
feeding back the test video signal to the micro-controller via an A/D converter, a receiver and a scaler of the LCD driving circuit, and
determining whether or not the test video signal is in trouble by comparing the test video signal from the micro-controller with the video signal fed back to the micro-controller; and
(c) if the operation mode of the LCD driving circuit is the normal operation mode, receiving the video signal from the PC, converting the video signal into a signal having a format suitable for the LCD panel, and outputting the video signal to the LCD panel to display the video signal from the PC on the LCD panel.